Field of the Invention
The apparatus used for early work in electrochromatography (EC) or electrophoresis in packed beds is described in Bloemendal, H., J. Chrom. 3 (1960) 1-10; Kunkel, H. G., and Trautman, R., Electrophoresis, Theory, Methods, and Applications, M. Bier, ed. (Academic Press, 1959), 225-262 and Porath, J. Sci. Tools 11 (2) (1964) 21-27. The early columns use either U-shaped tubes or specially constructed glass columns in which the electrodes are isolated from the column. These columns do not allow the application of the electrical field during the sample application or elution. These columns are usually operated in two steps. Samples are loaded on the column and the electrical field put on. Electrophoresis is done in the absence of any flow. After a period of electrophoresis the electrodes are removed and then flow was begun to elute the separated zones. A commercially manufactured electrophoresis column is described in Porath. This column is constructed so that the separation region containing the chromatography media is the annular space between two plastic cylinders. The top electrode is open to the separation region. The bottom electrode is isolated from the buffer coming out of the bottom of the separation system by a cylindrical membrane coaxial with the column separation region. The membrane used is a gel impregnated porous plastic. Nerenberg, S. T., and Pogojeff, B. A. (1969), Amer. J. Clin. Path. 51 (1960), 728-740 describe an electrochromatography column that utilizes a specialized end fitting. The end fitting uses a gel to isolate the electrodes from the chromatography column eluent. Rudge, S. R., Basak, S. K., and Ladish, M. R.. AIChE J., 39 (1993), 797-808 describes using chromatography column fittings containing platinum electrodes, but the electrodes are not isolated from the chromatography column eluent. U.S. Pat. No. 3,969,218 to Scott, the entire contents and disclosure of which is hereby incorporated by reference, also describes an electrophoresis process in which the electrodes are immersed in the column eluent. When the electrodes are immersed in the column eluent, gases, electrolytic products and pH changes generated at the electrodes contaminate the buffer throughout the column. Furthermore, proteins and macromolecules which are being separated using the column may react with the electrode. For these reasons, it is undesirable to have the electrode immersed in the column eluent.
Cole, K. D. and Cabezas, H., Jr., Appl. Biochem. Biotech. (1995) describe an electrochromatography column that has membranes located in side-arms but the electrodes are physically distant from the chromatography media. Although physically separating the electrodes from the chromatography avoids the problems of contamination, such separation limits the effectiveness of the electrodes.